Factor out internal dissipation as external addon dissipation module

[bhosale2]

Is your feature request related to a problem? Please describe.
Currently, the internal dissipation used to stabilize PyElastica simulations is a part of the Cosserat rod governing equations. This leads to the following 2 issues:

1. In over/critically damped cases, this can lead to a severe limitation on the timestep size, slowing down simulations.
2. Does not allow for a cleaner way to simulate an undamped rod, other than setting nu = 0 and crunching the damping steps for no reason.

Describe the solution you'd like
Following discussion with @armantekinalp, the dissipation step can be factored out of the Cosserat rod equations, and treated analytically, resulting in an exponential damper dissipation module, which is

1. Cleaner add-on module to undamped Cosserat rod.
2. Imposes no timestep restrictions on the simulator.
3. Allows for cleaner testing for other dissipation schemes (like filtering)

[bhosale2]

Closed via #114.